SonTek/YSI
ADVField/Hydra Operation Manual (September 1, 2001) 73
To begin a compass calibration using the compass commands, establish communications with the
ADV. Enter the command
Compass CAL
. The system will display basic instructions for the cali-
bration and give a continually updated output of heading, pitch, and roll. The compass is now in
multiple-point calibration mode and is collecting sample points. Rotate the compass slowly
through 360° at least twice, varying the pitch and roll as much as possible, so that a complete ro-
tation takes at least one minute to complete. When this has been done, press any key to terminate
the calibration. The ADV will respond with a calibration “score” similar to the following.
H9V9M12.3
This score is an indication of calibration quality. The values following the
H
and
V
should be high
(scale: 0 to 9). The value following the
M
should be low (scale: 0 to 100).
H
is the quality of the
horizontal calibration,
V
is the quality of the vertical calibration, and
M
is the amount of magnetic
distortion present. While scores will vary, if either
H
or
V
is below 6, or if
M
is greater than 30.0,
you should repeat the calibration. If the results do not improve, consider changing the ADV loca-
tion or modifying the mounting structure.
The compass calibration software follows an essentially identical procedure, and reports the same
calibration score. See the ADVField Software Manual for details.
4.7.6. Communicating Directly with the Compass
All communications for compass operation is done automatically by the ADV. In most cases, you
should not need to communicate directly with the compass. Should the need arise, you can com-
municate with the compass through the ADV by establishing communication and bypassing the
processor for a direct link to the compass.
To communicate with the TCM2, place the ADV in command mode. Send the following com-
mand to establish a direct link with the compass.
> echo compass
If the compass is operating properly, it should be continuously sending data to the ADV, which
will be redirected to the user. The data will look similar to the following:
$C143.2P3.4R5.4T24.5*3f
$C142.2P3.4R5.4T24.5*3e
The compass will now accept direct commands. For more details on communicating with the
compass, or for a copy of the compass operation manual, contact SonTek. When communications
with the compass is no longer desired, type three plus signs in succession (+++) or send a
BREAK
to return the ADV to command mode.
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